I have a slow-as-a-dog-in-summer Internet connection. What am I supposed to do?

Maybe skip this upgrade.

Because Apple will distribute Lion solely through the Mac App Store -- at least, that's the word so far -- you'll have to download it. And for those with skinny pipes to the Internet, that's a problem.

Anyone with a low-end DSL connection, for example, will need hours to download the 4GB Lion upgrade. Still stuck with dial-up? You're talking days.

If you want to calculate the time it will take to download Lion, plug "4GB" and your connection speed into this tool .

Like Snow Leopard , Lion won't run on the PowerPC architecture that Apple abandoned in early 2006 when it started the switch to Intel CPUs. So you're out.

If you have one of the earliest Intel-based Macs -- those first sold from the start of 2006 until the fall of that year -- Lion is also unavailable, because those machines were powered by 32-bit Core Duo chips.

Bottom line: If your Mac is more than 5 years old, you can forget about Lion.

To check the processor powering your Mac, choose "About this Mac" from the Apple menu.

I still rely on Rosetta to run very old PowerPC apps. What's the story for me? You may want to skip Lion.

Unlike Snow Leopard, which let users run apps compiled for PowerPC through Rosetta -- even though you had to download and install the software emulator yourself -- Lion doesn't even support the tool.

One end-around is to create two boot volumes on your Mac -- one with Lion, the other with Snow Leopard -- so you can access the PowerPC programs after launching the latter.

Other options: Upgrade the software (if an upgrade is available) to a version that runs on Intel systems, replace it with an alternative, or worst case, spring for virtualization software like Parallels Desktop, a copy of Windows 7 , and a Windows app substitute.

My Mac has just 1GB of memory. Is that enough for Lion? No. Lion requires 2GB, twice that of Snow Leopard.

It wasn't that long ago -- mid-2008 for the MacBook and iMac -- when Apple stocked systems with only 1GB, so even though yours has a Core 2 Duo processor and meets the CPU requirement, it might not cut it on RAM.

The lack of RAM shouldn't stop you from upgrading to Lion: It's easy and inexpensive to boost memory in a Mac. Crucial, one of the largest RAM sellers, prices a 4GB upgrade for the early-2008 MacBook at $60.

I stuck with Leopard. But I hear you need Snow Leopard to get Lion. What's that about? Blame Apple for pushing Lion through the Mac App Store.

Snow Leopard is the only edition of Mac OS X that supports the download market.

Apple's made it clear that you'll need to be running Snow Leopard, at least initially. "To upgrade on day one ... make sure you have the latest version of Snow Leopard," Apple says on its Lion site.

The "day one" reference leaves Apple enough wiggle room that it may offer an alternative to the Mac App Store download later, and thus give users running Leopard a way to migrate to Lion.

Or if you're betting Apple won't come through, then do a two-step upgrade now: first to Snow Leopard (for $29), then to Lion (for $30) next month. That's not ideal -- Mac owners have complained loudly, including on Apple's support forums -- but it's cheaper than a new Mac.